working commit(pass to compile)
use "CHECKTAG_before_bufferevent" tag to check diff
working commit
+ implement bufferevet to Libevent_glue.c, and pass compile
execute sample/bufferevent.k
fix mistake
[CONFIRMED] 'bufferevent.k' connects 'echoServer.k'
[TODO] support to use Konoha-instance in callback method.
Ideal situation is to treat Bufferevent instance in Libevent_glue.c.
Revert "[TODO] support to use Konoha-instance in callback method."

This reverts commit cbec8a0e1f67680b7e651e6cbedff227de0ed137.
bufferevent first step
little change
[FIX] support event_del() at socket shutdown or error